arch/um/kernel/skas/mmu.c

   1 /*
   2  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
   3  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   4  * Licensed under the GPL
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/sched.h>
   9 #include <linux/slab.h>
  10 #include <asm/pgalloc.h>
  11 #include <asm/pgtable.h>
  12 #include <asm/sections.h>
  13 #include <as-layout.h>
  14 #include <os.h>
  15 #include <skas.h>
  16
  17 static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  18                          unsigned long kernel)
  19 {
  20         pgd_t *pgd;
  21         pud_t *pud;
  22         pmd_t *pmd;
  23         pte_t *pte;
  24
  25         pgd = pgd_offset(mm, proc);
  26         pud = pud_alloc(mm, pgd, proc);
  27         if (!pud)
  28                 goto out;
  29
  30         pmd = pmd_alloc(mm, pud, proc);
  31         if (!pmd)
  32                 goto out_pmd;
  33
  34         pte = pte_alloc_map(mm, NULL, pmd, proc);
  35         if (!pte)
  36                 goto out_pte;
  37
  38         *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  39         *pte = pte_mkread(*pte);
  40         return 0;
  41
  42  out_pte:
  43         pmd_free(mm, pmd);
  44  out_pmd:
  45         pud_free(mm, pud);
  46  out:
  47         return -ENOMEM;
  48 }
  49
  50 int init_new_context(struct task_struct *task, struct mm_struct *mm)
  51 {
  52         struct mm_context *from_mm = NULL;
  53         struct mm_context *to_mm = &mm->context;
  54         unsigned long stack = 0;
  55         int ret = -ENOMEM;
  56
  57         stack = get_zeroed_page(GFP_KERNEL);
  58         if (stack == 0)
  59                 goto out;
  60
  61         to_mm->id.stack = stack;
  62         if (current->mm != NULL && current->mm != &init_mm)
  63                 from_mm = &current->mm->context;
  64
  65         block_signals();
  66         if (from_mm)
  67                 to_mm->id.u.pid = copy_context_skas0(stack,
  68                                                      from_mm->id.u.pid);
  69         else to_mm->id.u.pid = start_userspace(stack);
  70         unblock_signals();
  71
  72         if (to_mm->id.u.pid < 0) {
  73                 ret = to_mm->id.u.pid;
  74                 goto out_free;
  75         }
  76
  77         ret = init_new_ldt(to_mm, from_mm);
  78         if (ret < 0) {
  79                 printk(KERN_ERR "init_new_context_skas - init_ldt"
  80                        " failed, errno = %d\n", ret);
  81                 goto out_free;
  82         }
  83
  84         return 0;
  85
  86  out_free:
  87         if (to_mm->id.stack != 0)
  88                 free_page(to_mm->id.stack);
  89  out:
  90         return ret;
  91 }
  92
  93 void uml_setup_stubs(struct mm_struct *mm)
  94 {
  95         int err, ret;
  96
  97         ret = init_stub_pte(mm, STUB_CODE,
  98                             (unsigned long) __syscall_stub_start);
  99         if (ret)
 100                 goto out;
 101
 102         ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 103         if (ret)
 104                 goto out;
 105
 106         mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
 107         mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 108
 109         /* dup_mmap already holds mmap_sem */
 110         err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 111                                       VM_READ | VM_MAYREAD | VM_EXEC |
 112                                       VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
 113                                       mm->context.stub_pages);
 114         if (err) {
 115                 printk(KERN_ERR "install_special_mapping returned %d\n", err);
 116                 goto out;
 117         }
 118         return;
 119
 120 out:
 121         force_sigsegv(SIGSEGV, current);
 122 }
 123
 124 void arch_exit_mmap(struct mm_struct *mm)
 125 {
 126         pte_t *pte;
 127
 128         pte = virt_to_pte(mm, STUB_CODE);
 129         if (pte != NULL)
 130                 pte_clear(mm, STUB_CODE, pte);
 131
 132         pte = virt_to_pte(mm, STUB_DATA);
 133         if (pte == NULL)
 134                 return;
 135
 136         pte_clear(mm, STUB_DATA, pte);
 137 }
 138
 139 void destroy_context(struct mm_struct *mm)
 140 {
 141         struct mm_context *mmu = &mm->context;
 142
 143         /*
 144          * If init_new_context wasn't called, this will be
 145          * zero, resulting in a kill(0), which will result in the
 146          * whole UML suddenly dying.  Also, cover negative and
 147          * 1 cases, since they shouldn't happen either.
 148          */
 149         if (mmu->id.u.pid < 2) {
 150                 printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 151                        mmu->id.u.pid);
 152                 return;
 153         }
 154         os_kill_ptraced_process(mmu->id.u.pid, 1);
 155
 156         free_page(mmu->id.stack);
 157         free_ldt(mmu);
 158 }